District Judge Carlos A. Samour Jr. said in an order Thursday he would have to search outside the state and perhaps even the country to find jurors who haven't been exposed to extensive publicity.
Samour says he's confident the 12 jurors and 12 alternates selected in the trial of James Holmes are fair and impartial.
Opening statements are scheduled for Monday in Arapahoe County, just south of Denver, where the shooting took place.
Holmes has pleaded not guilty by reason of insanity to killing 12 people and wounding 70 in the July 2012 attack. His attorneys argued most prospective jurors were biased against Holmes.
Samour says the defence is responsible for much of the publicity.